1. Field
A reciprocating compressor, and more particularly, a reciprocating compressor including a gas bearing is disclosed herein.
2. Background
In general reciprocating compressors, a piston suctions and compresses a refrigerant while the piston is linearly reciprocated within a cylinder to discharge the refrigerant. Reciprocating compressors may be classified into connection-type reciprocating compressors and vibration-type reciprocating compressors according to an operation method, of the piston.
In such a connection-type reciprocating compressor, a piston is connected to a rotational shaft of the rotation motor through a connecting rod to compress a refrigerant while the piston is reciprocated within a cylinder. On the other hand, in such a vibration-type reciprocating compressor, a piston is connected to a mover of a reciprocating motor to compress a refrigerant while the piston is reciprocated and vibrated within a cylinder. Embodiments disclosed herein relate to the vibration-type reciprocating compressor. Thus, hereinafter, the vibration-type reciprocating compressor will be referred to as a reciprocating compressor.
The reciprocating compressor may be improved in performance when the cylinder and the piston are smoothly lubricated in a state in which they are air-tightly sealed. For this, according to the related art, a lubricant, such as oil, may be supplied between the cylinder and the piston to form an oil film, thereby sealing a space between the cylinder and the piston and also lubricating the cylinder and the piston. However, a separate oil supply to supply the lubricant is necessary. Also, if leakage of the oil occurs according to operation conditions of the compressor, the compressor may be deteriorated in performance. Also, as a space to receive a predetermined amount of oil is needed, the compressor may increase in size. In addition, as an inlet of the oil supply always has to be immersed in the oil, the compressor may be limited as to an installation direction thereof.
In consideration of the limitations of the oil lubrication type reciprocating compressor, as illustrated in FIGS. 1 and 2, a portion of a compression gas may be bypassed between a piston 1 and a cylinder 2 to form a gas bearing between the piston 1 and the cylinder 2. A plurality of bearing holes 2a, each of which may have a small diameter and through which the compression gas may be injected, may pass through an inner circumferential surface of the cylinder 2.
According to this technology, a separate oil supply to supply the oil may not be required between the piston 1 and the cylinder 2, simplifying a lubricating structure of the compressor. In addition, leakage of the oil according to the operation conditions may be prevented to uniformly maintain the performance of the compressor. Also, as a space to receive the oil is not required in a casing of the compressor, the compressor may be miniaturized and freely installed in various directions. Reference numeral 3 represents a plate spring, reference numerals 5a to 5c represent connecting bars, and reference numerals 6a and 6b represent links.
However, in the reciprocating compressor according to the related art, foreign substances mixed into a refrigerant gas may be introduced into a gas bearing, blocking the gas bearing. As a result, the refrigerant gas may not be supplied between the cylinder 2 and the piston 1, and thus, concentricity between the piston 1 and the cylinder 2 may be twisted, causing friction loss or abrasion while the piston 1 is reciprocated in a state in which the piston is closely attached to the cylinder 2. More particularly, when oil remaining in a refrigeration cycle is mixed with the refrigerant, and then, the mixture is introduced into the gas bearing of the compressor, foreign substances may block the gas bearing due to viscosity of the oil, deteriorating performance of the bearing. Also, when the oil is introduced between the cylinder 2 and the piston 1, the foreign substances mixed with the oil may adhere between the cylinder 2 and the piston 1, causing the friction loss or abrasion.
In consideration of this limitation, a bearing hole for the gas bearing may be increased in size to prevent the bearing hole from being blocked by the foreign substances. However, in this case, the compressed refrigerant gas may not be discharged into the refrigeration cycle, and thus, an amount of refrigerant introduced into the gas bearing may increase, increasing compression loss.